Servomotor



Jan. 9, 1951 E. A. ROCKWELL 2,537,433

SERVOMOTOR Original Filed April 11, 1941 5 Sheets-Sheet l INVENTOR Edward A. Fwckweii am tm m ATTORNEY Jan. 9, 1951 E. A. ROCKWELL SERVOMOTOR 5 Sheets-Sheet 2 Original Filed April 11, 1941 INVENTOR Edward H. Rockwell BY v ATTORNEY Jan. 9, 1951 E. A. ROCKWELL SERVOMOTOR 5 Sheets-Sheet 5 Original Filed April 11, 1941 IIIIAYIIIIIIIIII a k 6 w m R M m m m m A m Wm A m J EB Jan. 9, 1951 E. A. ROCKWELL SERVOMOTOR 5 Sheets-Sheet 4 Original Filed April {L1, 1941 INVENTOR Edward $2. liar/swell ATTORNEY Jan. 9, 1951 E. A. ROCKWELL 2,537,483

SERVOMOTOR Original Filed April 11, 1941 5 Sheets-Sheet 5 70 939 9592 97 38 i 79 gl 9;; 94 74 II '11. 1 8 .1 72 75 7/ 4 88730 INVENTOR Edward AJi/oc/vwe-ZZ ATTORNEY Patented Jan. 9, 1951 UNITED STATES PATENT OFFICE Edward A. Rockwell, Cleveland, Ohio Application February 17, 1943, Serial No. 476,245, which is a division of application Serial No. 388,003, April 11, 1941. Divided and this applica'tion February 22, 1945, Serial No. 579,294

7 2,388,220, granted October 30, 1945, which is also a division of my application upon Power Intensi- Another object is to provide a follow-up mechanism including valves of the above character. Still another object is to provide a valve mechanism of the above type, involving an operating plunger for operating a valve mechanism from the hydraulic inlet and in which the liquid fromthe hydraulic inlet is conducted from the latter to the outlet of the servo device around the end of the plunger. a valve operating plunger of the above character; having differential areas arranged to increase the liquid pressure on the output side of said plunger. Still another object is to provide a valve device as above referred to, having a hydraulic connection to said output as well as to thehydraulic liquid from the inlet. Further objects of my: invention will appear from the detailed description of the same hereinafter.

' While my invention is capable of embodiment in many different forms, for the purpose of illustration I have shown only one form thereof.

in the accompanying drawings in which- Fig. l is a perspective view showing the parts of an automobile chassis to which my invention is applied;

Fig. 2 is an elevation partly in section of a. master cylinder used in accordance therewith; Fig. 3 is a plan view of a power unit made in accordance with my invention, with the air filter removed;

- Fig. 4 is an end elevation of the same;

: Fig. 5 is a longitudinal section thereof taken on line. 55 of Fig. 3;

Fig. 6 is a vertical section taken on line 6 -6 A further object is to provide 2 of Fig. 5, showing the valve-operating lever and diaphragm valves. operated thereby;

Fig. 7 is a detailed section showing the mounting of said valve-operating lever taken on line, l -l of Fig. 6; and

Fig. 8 is a vertical sectionoi a modified air inlet device. 7 g 1 Referring to the drawings, I'have shown a pedal I mounted one fixed pivot 3 at any desired point on an automobile chassis (not shown which has an operating link 4 attached to said pedal, which in turn is connected to an operate;

ing lever 5 of a master sylinder 5. The master: cylinder 6 may be constructed in accordance with any desired type of master cylinder but may, for example, be constructed in accordance with; the master cylinder shown in the Loughead- Patent No. 1,707,063, granted March 26, 1939;; The operating lever 5 may be mounted on a shaft 5 which extends into said master cylinder, and on said shaft '1', within said master cylinder 6, there is an operating arm 8 which bears upon a piston 9 that extends into a cylinder Ill which is in communication with the liquid in the master cylinder 6 by meansof a port H, which port ll; is uncovered in the retracted position of the: pistone. The said master: cylinder i5 thus acts. as a storage chamber for the hydraulic liquid and is provided with a cover l2 having a vent I3,

said cover having the usual removable filler-cap M. The cylinder It has the usual spring l5 ion retracting the piston 9 and a flexible discharge, conduit ll; which leads to a screw-threadedv fitting 16a on a power unit ll, said power unit l! having a flexible discharge pipe it which,

leads by any desired branch pipe to Wheel 63 1-, inders l 8 located on the four wheelsof the auto- L mobile chassis (not shown) so as to operate the} around a steering column 340i the automobile chassis. Also secured to said plunger housing 25}. there is a rear shell 35 secured in place by screws, 36. The said rear shell 35, by means of screws; 37, clamps in place a main diaphragm 38 against? a forward shell 39 which has a screw-threaded, sleeve 4% secured-thereto. and which communi-g relative location of the? cates by a fitting 4| with a flexible pipe 42 which leads to a manifold 43 of the internal combustion engine mounted on said chassis for driving the automobile. The sleeve contains a check valve 43a provided with peripheral notches 43b and having a cylindrical valve seat 430 cooperating therewith.

The liquid forced manually out of the master cylinder 6 and received by the power unit I! from the pipe I6, enters through a coupling member 44 in said plunger housing 25 into a valve chamber 45. This chamber 45 has a peripheral recess 45a into which there is sprung a liquid distributor plate 45b having near the edge thereof a marginally arranged series of notches 450 to distribute the force of the incoming liquid, thus avoiding undesirable impact on the inlet valve. The initial operation of the brakes by the manual force applied, causes the liquid to flow into a chamber 46 in a plunger sleeve 4'! having ports 48 leading to a cylindrical chamber 49. The plunger sleeve 41 has a U-shaped rubber seal 50 and carries within the same a valve stem or plunger 5! having a head 52 thereon, beneath which there is a rubber gasket 53 arranged to act as a compensating inlet valve, the seat for which is a shoulder 54 on the plunger sleeve 41, so that when thus seated the hydraulic liquid, which in the initial operation of the apparatus is conveyed from the cylinder 49 by a port 55 to a pressure cylinder 56 and thence to the brakes through the pipe I8, is cut off by said valve 53, 54 so as thereafter to apply the power from the power unit. It will be noted that the valve stem 5| or plunger serves as a supporting guide for the plunger sleeve 41 which is reciprocable to some extent on said valve stem. The movement of the plunger sleeve 41 to the right, in Fig. 5, is limited by a stop 51 formed on the interior of the coupling 44 and the movement of said plunger sleeve 4'! to the left of said figure is limited by a plunger sleeve 58 which is screwthreaded on the said stem 5 I.

The plunger sleeve 58 has thereon a plunger 59 and an annular rubber seal 60. The said plunger 59 operates in a cylindrical chamber 61 which carries a coil spring 62 normally forcing the plunger 59 to the right so as to unseat the valve 53, 54, which when open compensates the liquid on the two sides of the valve. The other end of said spring 62 rests against a sleeve 63 located tightly in the end of the chamber GI, said sleeve having a cap ring 64 and a leather gasket 65 around a rod-shaped plunger 66 carried within a bushing 61 within the sleeve 63. The said rod-like plunger 66 bears at its rear end against the plunger 59 and at its forward end bears against the end of a valve-operating lever 68, which in turn operates a spring 69 located around a guide rod T0 having a screw-threaded reduced end II passing through plates I2 and i3 clamped around an opening I4 in the diaphragm 30, where it is held in place by a nut I5. The plates I2 and I3 are secured together by screws 13a at the periphery thereof and screws 7312 located on opposite sides of a laterally offset portion I30 of the plate I2. The said lever 68 is supported by a pivot I6, which can be placed at any desired point along said lever to obtain the desired lever ratio, on a rod 17 having a screw-threaded end 18 passing through the plate I3 to which it is tightly held by a nut I9. The other end of the lever 68 has a pivot 80, by means of which it is pivotally connected to a valve-operating sleeve 8| screwthreaded on a valve stem 82 having a vacuum or outlet valve head 83 connected thereto and which carries within the same a rubber washer 84. The said rubber washer seats upon an annular valve seat 85 which is clamped to a subsidiary diaphragm 66 supported by screws 81 and a clamping ring 88 from the plate I2. This clamping to the diaphragm 85 is accomplished by means of a clamping plate 89 held in place by a valve sleeve 99 screw-threaded to the annular valve seat 85. A coil spring 9| bears at one end against the clamping plate 89 and at the other end against the plate I3 so as to normally force the valve sleeve 90 to the left of Fig. 5 and thus seat a rubber washer 92 of an air valve or inlet valve 93 against an annular valve seat 94 carried in the plate I3. It will be noted that the valve sleeve 90 has air ports 95 leading from within the sleeve to the interior of the shell 35. The air which is admitted to the interior of the shell 35 through the valve 94 is received from openings 96 communicating with a chamber 9! between the plates I2 and 13, said opening 96 being provided in a screw-threaded plug 98, havin a leather gasket 98a, passing through the plates l2 and I3. A hollow plunger 99 is screw-threaded to the plug 98 which has a central passageway I09 communicating with a longitudinal passageway IOI in the plug 93. This hollow plunger 99 clamps the plate I3 against a shoulder I02 on the said plug 98. Ports I93 in the said plunger 99 communicate with a chamber I94 in the said plunger housing 25 which has an air vent I05 leading to the outer air through a tube I050. leadin to an air filter casing I95b, filled with horse-hair, having a headed sleeve e, with openings 805d, screwthreaded to the tube I050; and provided with a shoulder I956 against which a plate [05 rests, which has air vent openings I059. The chamber 6| is also connected to said vent I95 by a passageway i06 located between the chambers GI and I04. Furthermore, the said chamber I04 has a bushing I09 and outside the same a sleeve support IIII, which is tightly carried within the chamber I04. The end of the sleeve I I0 is screw-threaded to a cap III which acts as a stop in the movement of the plate I3 and also serves to hold in position a leather seal II2 against the outside of the hollow plunger 99. Within the hollow plunger 99 there is a rod H3, operating in an air transfer passage Il3a, the rear end of which rod is screwthreaded into a plug II4 acting as a closure for the cylindrical chamber 56. On the forward end of said rod H3 there is a head H5 holding in place a washer H6 which acts as a support for a sprin II'I around the rod II3, the other end of said spring l I? being supported against a headed sleeve IIB which in turn rests against a shoulder H9 in the hollow plunger 95. The said headed sleeve H8 carries a washer H90. and, furthermore, is screw-threaded to a plunger stem I20 passing through a guiding sleeve I2I held in place in the chamber 56 by a screw I22. The said plunger I29 carries rubber seals 123 and I24 between which there is carried a coil spring I25 on the plunger stem I20, which in turn has a plunger head I26 adjacent to the rubber seal I24, which exerts a pull inducted by the diaphragm 38 to place the liquid in the chamber 55'under increased pressure due to the relative sizes of the diaphragm 38 and the plunger I 26.

In assembing the power unit it will be understood that the diaphragm 38, plates l2 and I3 and the valve elements together with the operating lever 68 mounted thereon, can be made into one assembly and the plunger mechanism made into another assembly and that these two assemblies can then be assembled together while at the same time securing the shells 35 and 39 thereto.

In Fig. 8 I have shown a modified air inlet device in which there is provided means for adjusting the amount of air admitted at different altitudes at which the automobile is operated and so as to control the outlet pressure of the apparatus. In this figure I have shown connected to the air vent port I a screw-threaded tube I21 having a flared portion I28 provided with a flange I29 against which there is clamped a rubber diaphragm I39, having a central aperture I3I, by means of screws I32 passingthrough the diaphragm into said flange I29 and passing through a flange I33 on an air valve housing I34 provided with air ports I35. The upper portion of the housing E34 has a screw-threaded opening I38 through which there is arranged to pass an adjusting screw I31 provided with a knurled head I38. On the screw I31 there is a lock-nut I39 so as to hold in place above the housing I34, an air filter shell I49 filled with horse hair and which has a depending rim I4I s0 arranged as to leave an annular air inlet I42 between the same and the flanges I29 and I33. The adjusting screw I31 has a rounded lower end I43 which is received in a recess I44 in an air valve plate I45 having a downwardly directed rim I48, the air valve plate I45 being pressed upwardly by a compressed spring I41 which is supported at its lower end on a shoulder I48 within the tube I21. The rim I48 is arranged to be adjusted into or out of contact with the diaphragm I38 so as to provide an air passageway I49 between the valve plate I45 and said diaphragm I38. The diaphragm I38 is supported in its uppermost position by a supporting ring I59 which is dished andthence to within the rear diaphragm shell 35 on the right of the diaphragm 38. This exerts a hydraulic pressure in the chamber 58 which, by its reaction, has a tendency to move the diaphragm 38 in the, opposite direction to its direction of movement by the manual force applied. The effect of this incoming air from the valve 93 is balanced between said valve 93 and the diaphragm 88so as to prevent the valve 93 from being suddenly opened by said incoming air. It will be noted, furthermore, that the air may be admitted, in this way, to the chamber within the shell 35 in any desired increments and that between the accession of such increments to the right of the diaphragm 38 the two valves 83 and 93 will be in lapped or closed position due to the pneumatic pressure, above referred'to, tending to move the diaphragm86 while the valve 93 is still open, the diaphragm 38 upwardly so as to receive a coil spring I5I seated at its lower end on a shoulder I52 in the inside of the flared portion I28v of the tube I21. When operating the automobile at high altitudes the spring I5I will be in its position of full extension with the plate I adjusted out of contact with the diaphragm I38, whereas at lower altitudes or where the output pressure applied to the brakes is to be lessened, the plate I45 will be adjusted into contact with the diaphragm I30 so as to compress the spring I5I more or less, as desired, according to the position of the screw I31.

In the operation of the apparatus, when it is desired to apply the brakes the pedal I is moved to the left, in Fig. 1, whereupon some of the liquid from the master cylinder 6 passes from the pipe I6 through the valve chamber 45, ports 48, port 55, chamber 58 and pipe I8 to the Wheel brake cylinders I3 so as to move the brake shoes 28 and 2| up into position, for applying the main braking effect. A further increase of this manual pressure from the pipe I8 will cause the piston 59 to move forwardly in the chamber 8|, thus closing the valve 53, 54 and simultaneously operating the lever 38 so as to move the valve 83 into closed position while moving forwardly, slightly, the plates 12 and 13 as well as the diaphragm 38 through the intermediary of the spring 89. Further increase of the manual pressure, resulting in further movement of the plunger rod 68 in this direction, results inopening the air inlet valve 93 due to the further movement of the lever 68 and the yielding of the dia-- phragm 85. The opening of the valve 93 admits the air to the desired extent from the vent I85, ports I83, chamber I80, passageway IUI, ports 96 III LII

ill

downwardly in Fig. '1 in anyone position of power application in which the pedal I is held. In other words, as the diaphragm 38 moves to the left, in Fig. 5, the pivot 18 is carried thereby, and upon cessation of movement of the pedal I,

will still continue to move to the left slightly as the left hand end of the plunger I38 is then a stationary pivot. At this time, also, a slight movement of the lever 68 affects the valves 83 and 93, to move them into lapped position. Consequently, the said valves can apply a modulated degree of pressure to the right side of the diaphragm 38, as desired, while transmitting through said valves and lever 88 to the manual means a reaction due to the differential pressures on opposite sides of the valve 84, supported n the diaphragm 88. Similarly, the air may be withdrawn by increments in the same manner from the right of the diaphragm 38 through the opening of the valve 83 to the desired extent for this purpose, b lessening the pressure exerted on the pedal I. When the atmospheric air pressure has been admitted to the desired extent to the right of the diaphragm 38,

this action will be accompanied by the movement of the hollow plunger 99 to the left in Fig. 5, against the compression of the spring "I i1 so that the plunger head I 28 will move to the left in said figure, thereby placing the liquid which is in the chambers 56 and 49 under a pressure to the extent desired and as determined by the manual pressure from the pedal I, thus applying the power pressure through the pipe Iii-to the brakes and exerting the reaction from the cham' here 55 and 49 on the foot through the pedal I. This pressure exerted on the brakes may be of any desired maximum but may, for example, be about 1500 lbs. per square" inch, whereas the manual pressure applied from the master cylinder may, for example, be from 0 to 600 lbs. per square inch, or any other ratio of these or other pressures can be obtained, as desired. In view a part of the liquid used in applying the brakes,

even when the power isbeing applied about 40% of the liquid in applying the brakes is provided accuse by the foot pressure. that the volume received in the right-hand end of the bore in which the plunger 4? slides is smaller than the volume delivered by the pipe [8, thus providing for a small pedal travel. In fact, at times the foot pressure applied to the brakes can be increased without substantially moving the foot forwardly. Thus, an effective modulation of the pressures applied to the brakes,

is obtained at all times, by the manual pressure or the manual pressure and the Power pressure proportionally thereto. However, in this power unit, whatever force is supplied manually by the foot pedal is entirely oliset by an equal and opposite force from the power piston :29 so that, consequently, all the brake-applying force for operating the brakes, when the power is on, is derived entirely from the power plunger 120. This apparatus is, thus, a full power unit. For

these reasons, also, the brake is practically as effective, irrespective of considerable variations in the vacuum from the manifold, due to the direct connection just referred to and the large size of the diaphragm 33. Furthermore, it will be noted that at all times a reaction passes from the liquid applied in the operation of the brakes back to the foot, through the pipe it either from the liquid in the chamber 49 through the valve 53, 54 when this valve is open at the beginning or towards the end of the application of manual pressure, or from the chamber 49 on the plunger sleeve 4? when said valve is closed, thereby making the degree of application of the brakes readily ascertainable without th pedal being moved towards its off position. Also, the actuation of the brakes is made more effective by reason of the coordination of the travel of the pedal l to the movement of the brakes, as it will be evident that the movement of the brake liquid is coordinated to the travel of the liquid supplied from the master cylinder. In order to throw the brakes out of operation, the manual pressure on the pedal is fully released, whereupon the spring 69 opens the valve 33 and allows the valve 93 to close and the springs ill and i525 withdraw the diaphragm 38 to the right, thus admitting vacuum thence through the ports 95 to the'right of the diaphragm 38. This action is accompanied by the unseating of the valve 53, thus restoring the parts again to their original positions and compensating for any possible loss of which the automobile is operating or according to th amount or the maximum output pressure desired to be applied to the brakes. In other words, when the automobile is operating at a high altitude, with consequent lessened atmospheric pressure, the plate M will be adjusted upwardly to a position away from contact with; When, however, the auto mobile is operating at a lower altitude, or when it is desired to decrease the maximum available pressure output supplied to the brakes, the plate the diaphragm 5'33.

145 will be adjusted downwardly by the screw I31 until it contacts with the diaphragm 133 or until, by further adjustment, it compresses the spring l5i to the point desired. Of course, whenv the apparatus is being operated to apply pressure to the brakes, the incoming air will in any case pass through the air inlet I42, p orts' l;35,,

This is owing to thefact.

8. passage I49 and thence into the tube 121, thus applying to the diaphragm I a degree of the vacuum existing at the right of the diaphragm 38, Fig. 5. When the valve plate has been adjusted into contact with the diaphragm $30, the incoming air pressure will move the diaphragm I30 downwardly by compressing the spring 15!.

It will be understood that instead of supplying a vacuum to the fitting 4| this may be a vent and that instead of the port I05 being a vent this may be connected to a source of superatmospheric air pressure.

While I have described my invention above in;

'. detail I wish it to be understood that many changes may be made therein without depart-. ing from the spirit of the same.

I claim: 1. A servomotor structure, comprising a by-:-

,draulic plunger having a chamber, an inlet to receive a liquid for operating the plunger, an outlet having a hydraulic communication extending from said outlet to said inlet along the outside and the end of the plunger, a hydraulic liquid cut-oil valve operated by the plunger, a connec tion on the structure adapted to be connected to a source of fluid pressure, an enclosure, and a. movable wall in the enclosure having a hydraulic connection to the outlet and a pneumatic valve associated with said wall and operated by said, plunger for controlling the movement of said wall by said source of fluid pressure,

2. A servomotor structure, comprising a hydraulic plunger having a chamber, an inlet to receive a liquid for operating the plunger, an outlet having a hydraulic communication extending from said outlet to said inlet along the out-. side and the end of the plunger, a hydraulic liq-5; uid cut-01f valve operated by the plunger, a connection on the structure adapted to be connected to a source of fluid pressure, an enclosure, and a. movable wall in the enclosure having a hydraulic connection to the outlet and a pneumatic valve associated with said wall and operated by said plunger for controlling the movement of said wall by said source of fluid pressure, said cut-01f valve. being carried by said plunger. I

3. A servomotor structure, comprising a hy-c draulic plunger having a chamber, an inlet to receive liquid for operating the plunger, an out-. let having a hydraulic communication extend-J ing from said outlet to said inlet along the outside and the end of the plunger, a hydraulic liq-".- uid cut-ofi valve operated by the plunger, a coin nection on the structure adapted to be connected to a source of fluid pressure, an enclosure, a mov-v able wall in the enclosure having a pneumatic valve associated with said wall and operated by said plunger for controlling the movement of said wall by said source-of fluid pressure, said plunger having effectively acting thereon differential input and output pressure areas arranged to increase the liquid pressure on the output side. thereof by the movement of said plunger, and a; hydraulic outlet connected to said output area.

4. A servomotor structure comprising a hydraulic plunger having a chamber, an inlet to re ceive a liquid for operating the plunger, an out-- let having a hydraulic communication extending. from said outlet to said inlet along the outside, and the end of the plunger, a hydraulic liquid cut-oil valve operated by the plunger, a connection on the structure adapted to be connectedto. a source of fluid pressure, an enclosure, a mov--- able wall in the enclosure having a pneumatic,

valve associated with said wall and operated by said plunger for controlling the movement of said wall by said source of fluid pressure, said outofi valve being carried by said plunger, said plunger and cut-off valve having effectively acting thereon differential input and output pressure areas arranged to increase the liquid pressure on the output side thereof by the movement of said plunger, and a hydraulic outlet connected to said output area. I

5. A servomotor structure comprising a hydraulic plunger having a chamber, an inlet to receive a liquid for operating the plunger, a hydraulic liquid cut-01f valve operated by the plunger, a connection on the structure adapted to be connected to a source of fluid pressure, an enclosure, and a movable wall in the enclosure having a pneumatic valve associated with said 'wall to control the movement of'the wall, said pneumatic valve being ccnnected to said plunger for movement by the plunger in opposite direction to the plunger when the cut-01f valve is closed.

6. A servomotor structure comprising a hydraulic plunger having a chamber, an inlet to receive a liquid for operating the plunger, a hydraulic liquid cut-oil valve operated by the plunger, a connection on the structure adapted to be connected to a source of fluid pressure, an enclosure, and a movable Wall in the enclosure having a pneumatic valve associated with said wall to control the movement of the wall, said pneumatic valve being connected to said plunger for movement by the plunger in opposite direction to the plunger when the cut-off valve is closed, said cut-off valve having a valve-operating element on said plunger.

7. A servomotor structure comprising a hydraulic plunger having a chamber, an inlet to receive a liquid for operating the plunger, a hydraulic liquid cut-01f valve operated by the plunger, a connection on the structure adapted to be connected to a source of fluid pressure, an enclosure, a movable wall in the enclosure having a pneumatic valve associated with said Wall to control the movement of the wall, said pneumatic valve being connected to said plunger for movement by the plunger inopposite direction to the plunger when the cut-01f valve is closed, said plunger having effectively acting thereon differential input and output pressure areas arranged to increase the liquid pressure on the output side thereof by the movement of said plunger, and a hydraulic outlet connected to said output area.

. 8. A servomotor structure comprising a hydraulic plunger having a chamber, an inlet to receive a liquid for operating the plunger, a hydraulic liquid cut-off valve operated by the plunger, a connection on the structure adapted to be connected to a source of fluid pressure, an enclosure, a movable wall in the enclosure having a pneumatic valve associated with said wall to control the movement of the wall, said pneumatic valve being connected to said plunger for movement by the plunger in opposite direction to the plunger when the cut-ofi valve is closed, said outofi valve having a valve operating element on said plunger, said plunger and cut-01f valve having effectively acting thereon differential input and output pressure areas arranged to increase the liquid pressure on the output side thereof by the movement of said plunger, and a hydraulic outlet connected to said output area.

9. A servomotor structure, comprising a hydraulic plunger having a chamber, an inlet to a 10 receive liquid for operating the plunger, an outlet having a hydraulic communication extending from said outlet to said inlet along the outside and the end of the plunger, a hydraulic liquid cut-off valve operated by the plunger, a connection on the structure adapted to be connected to a source of fluid pressure, an enclosure, a movable wall in the enclosure having a pneumatic valve associated with said wall and operated by said plunger for controlling the movement of said wall by said source of fluid pressure, said plunger having effectively acting thereon differential input and output pressure areas arranged to increase the liquid pressure on the output side thereof by the movement of said plunger, and a hydraulic outlet connected to said'output area having a hydraulic connection to the movable wall. a 10. A servomotor structure comprising a hydraulic plunger having a chamber, an inlet to receive a liquid for operating the plunger, an outlet having a hydraulic communication extending from said outlet to said inlet along the outside and the end of the plunger, a hydraulic liquid cut-oif valve operated by the plunger, a connection on the structure adapted to be connected'to a source of fluid pressure, an enclosure, a movable wall in the enclosure having a pneumatic valve associated with said wall and operated by said plunger for controlling the movement of said wall by said source of fluid pressure, said cut-off valve being carried by said plunger, said plunger and cut-off valve havingeifectively acting thereon differential input and output pressure areas arranged to increase the liquid pressure on the output side thereof by the movement of said plunger, and a hydraulic outlet connected to said output area having a hydraulic connection to th movable wall. I

11. A servomotor structure comprising a followthrough hydraulic plunger having a chamber, an

inlet to receive a liquid for operating the plunger,

a hydraulic liquid cut-off valve operated by the plunger, a connection on the structure adapted to be connected to a source of fluid pressure, an enclosure, a movable Wall in the enclosure having 'a pneumatic valve associated with said wall to control the movement of the wall, said valve being connected to said plunger for movement by the plunger in opposite direction to the plunger when the cut-01f valve is closed, said plunger having effectively acting thereon differential input and output areas arranged to increase the liquid pressure on the output side thereof by the move-, vment of said plunger, and a hydraulic outlet cona hydraulic saidvalve being connected to said plunger for movement by the plunger in opposite direction to the plunger when the cut-01f valve is closed, said cut-01f valve having a valve-operating element on said plunger, said plunger and cut-off valve having effectively acting thereon differential input and output pressure areas arranged to increasefthe liquid pressure on the'output side thereofby the movement of said plunger, and a hydraulic outlet connected to said output area having a hydraulic connection to the movable wall. 13. A servomotor structure comprising, an inlet for receiving hydraul c liquid, a hydraulic liquid cut-off valve operated by said liquid, a connection on the structure adapted to be connected to a source of fluid pressure, an enclosure, 2, movable wall in the enclosure, a pneumatic valve connection on the structure adapted to be connected to a source of fluid pressure, an enclosure, a movable wall in the enclosure, a pneumatic valve controlled by said hydraulic liquid for admitting the fluid pressure to said wall, means connecting with said cut-off valve and pneumatic valve to Opel" ate the pneumatic valve on closure of the cut-oil "valve, a plunger device connected to said wall -having a cylinder, a bushing around said plunger device acting as a guide for said device, an annular support between the bushing and the enclosure, and an annular cap for said bushing and support to act as a stop for said movable Wall.

15. A servomotor structure comprising, an inlet for receiving hydraulic liquid, a hydraulic liquid cut-01f valve operated by said liquid, a connection on the structure adapted to be connected to a source of fluid pressure, an enclosure, a movable wall in the enclosure, a pneumatic valve controlled by said hydraulic liquid for admitting the fluid pressure to said wall, means connecting with said cut-off valve and pneumatic valve to operate the pneumatic valve on closure of the cut-oil valve, a plunger device connected to said wall having a cylinder, a bushing around said plunger device acting as a guide for said device, and an annular cap for said bushing located inside said enclosure to act as a stop for said movable wall.

16. A servomotor structure comprising, an inlet for receiving hydraulic liquid, a hydraulic liquid cut-off valve operated by said liquid, a connection on, the structure adapted to be connected to a source. of fluid pressure, an enclosure, a movable wall in the enclosure, a pneumatic valve controlled aby said hydraulic liquid for admitting the fluid pressure to said Wall, means connecting with said cut-oil" valve and pneumatic valve to operate the pneumatic valve on closure of the cut-off valve,

12 a plunger device connected to said wall havin a cylinder, at bushing around said plunger device acting as a guide for said device, an annular support between the bushing and the enclosure, and

the pneumatic valve on closure of the cut-off valve, a plunger device connected to said wall having a cylinder, a bushing around said plunger device acting as a guide for said device, and an annular cap for said bushing to act as a stop for said movable Wall, said plunger being constructed and arranged to exert a pressure force in a direction to maintain the cut-off valve in the closed position.

18. A servomotor structure comprising, an inlet for receiving hydraulic liquid, a hydraulic liquid cut-off valve operated by said liquid, a connection on the structure adapted to be connected to a source of fluid pressure, an enclosure, a movable wall in the enclosure, a pneumatic valve controlled by said hydraulic liquid for admitting the fluid pressure to said wall, means connecting with said cut-oil valve and pneumatic valve to operate the pneumatic valve on closure of the cut-ofi valve, a plunger device connected to said wall having a cylinder, a bushing around said plunger device acting as a guide for said device, an annular support between the bushing and the enclosure, and an annular cap for said bushing and support to act as a stop for said movable wall,

said plunger being constructed and arranged to exert a pressure force in a direction to maintain the cut-off valve in the closed position.

EDWARD A. ROCKWELL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,260,491 Stelzer Oct. 28, 1941 2,353,755 Price July 18, 1944 2,398,252 Rockwell Apr. 9, 1946 FOREIGN PATENTS Number Country Date 412,965 Great Britain July 6, 1934 

